:Product: Weekly Highlights and Forecasts :Issued: 2004 Jul 20 2212 UTC # Prepared by the US Dept. of Commerce, NOAA, Space Environment Center # Product description and SEC contact on the Web # http://www.sec.noaa.gov/weekly.html # # Weekly Highlights and Forecasts # Highlights of Solar and Geomagnetic Activity 12 - 18 July 2004 Solar activity ranged from moderate to high. The period began with occasional low to moderate-level M-class flares on 12 – 13 July from new Region 649 (S10, L=044, class/area, Fki/530 on 16 July). New Region 646 (N13, L=169, class/area, Dai/220 on 13 July) emerged on 11 July and went into a rapid growth phase on 12 – 13 July. Activity levels increased to high on the 13th as developing region 646 produced three strong flares – two M5s and an M6. Lower M-class activity was also observed in Region 649. Two asymmetrical full-halo CMEs were observed from Region 646 due to the M-class activity. High levels continued on the 14th with another M6 flare from Region 646. New growth was observed in Region 649 on 15 July and a complex delta magnetic configuration formed in the trailing spots. Activity levels remained high on 15 – 17 July as Region 649 produced six X-class flares, the largest an X3.6/3b at 16/1355 UTC. No highly structured CMEs were observed from any of the major flares observed in Region 649. New Region 652 (N05, L=346, class/area, Fkc/1370 on 18 July) rotated into view on 16 July and produced low to moderate level C-class activity. Though still near the east limb, a strong delta structure was evident. Solar wind data were available from the NASA Advanced Composition Explorer (ACE) spacecraft during most of the summary period. The period began under the influence of a coronal hole high speed stream. Solar wind speeds were observed at 550 to 600 km/s and persisted at this velocity through early on the 14th. Solar wind speed gradually declined to near 400 km/s when late on 16 July, a shock passed the ACE satellite and wind velocity increased sharply to near 600 km/s. This transient was believed to have been the result of the full halo CME activity seen on 13 July. Solar wind speed gradually decreased to 400 km/s through the end the period. IMF Bz was generally in the +5 to –5 nT range with a brief period of sustained southward Bz to –15nT beginning late on the 16th. There were no greater than 10 MeV proton events at geo-synchronous orbit during the summary period. The greater than 2 MeV electron flux at geosynchronous orbit remained below the high threshold. The geomagnetic field ranged from quiet to major storm levels. The first two days of the summary period were dominated by quiet to active geomagnetic conditions due to the influence of the coronal hole high speed stream. Activity levels decayed to generally quiet to unsettled conditions with isolated active periods. The onset of the transient on 16 July resulted in active to major storm levels early on 17 July. Thereafter, through the end of the summary period, the field was quiet to unsettled. Forecast of Solar and Geomagnetic Activity 21 July - 16 August 2004 Solar activity is expected to range from low to high. Regions 649 and 652 are both expected to produce further M and X-class activity early in the period. Old Region 646 is due to return on 29 July and could produce isolated M-class flare activity through 12 August. A greater than 10 MeV proton event is possible. The greater than 2 MeV electron flux at geosynchronous orbit is expected to reach high levels on 26 – 27 July due to a recurrent coronal hole high speed stream. The geomagnetic field is expected to range from quiet to active levels with minor storm periods at high latitudes. Unsettled to active conditions with high latitude minor storm periods are possible on 25-26 July as a recurrent coronal high speed stream rotates into a geoeffective position. At the time of this writing, a CME associated with an M8 flare in Region 652 appears to be at least partially Earth directed; consequently, minor to major storm levels are possible on 23 July. Region 652 is a very large and complex sunspot group with good potential for geoeffective CMEs during the first week the forecast period.